The present invention relates to the use of selected polydiorganosiloxanes in fabric softener compositions and to fabric softener compositions comprising these polydiorganosiloxanes.
Fabric softener compositions which can be added to the rinse water when washing household laundry are well known as xe2x80x9csoftenersxe2x80x9d. Such compositions normally comprise, as active substance, a water-insoluble quaternary ammonium compound. Commercially available fabric softener compositions are based on aqueous dispersions of water-insoluble quaternary compounds. In recent times, there has been increasing interest in biodegradable active substances. Such compounds are, for example, esters of quaternary ammonium compounds, so-called xe2x80x9cesterquatsxe2x80x9d, which have at least one long-chain hydrophobic alkyl or alkenyl group interrupted by carboxyl groups. Such compounds are described, for example, in EP-A-0 239 910 or WO 95/24460.
Particularly suitable esters of quaternary ammonium compounds correspond to the formula 
in which
R is the aliphatic radical of tallow fatty acid, in particular a mono- or polyunsaturated aliphatic C17 radical.
Active substances in fabric softener compositions which impart a good soft handle to the treated textile have the disadvantage that they lower the water absorbency of the textile fabric, in particular cotton fabric treated with the fabric softener In particular, this disadvantage of low rewettability is highly pronounced in the case of the aforementioned esterquats.
The object of the present invention is thus to find an additive for fabric softener compositions which improves the rewettability of the treated textiles and which at the same time does not impair the other positive properties, such as soft handle and static properties of the treated items.
Surprisingly, it has been found that certain polysiloxanes satisfy these prerequisites.
The present invention thus provides for the use of fabric softener compositions comprising
(a) as active substance, a quaternary ammonium compound of the formula (1); and
(b) a nitrogen-free polydiorganosiloxane having terminal silicon-bonded hydroxyl groups; for the treatment of textile fibre materials.
The polydiorganosiloxanes are linear or practically linear siloxane polymers having terminal silicon-bonded hydroxyl radicals. Polydiorganosiloxanes of this type have about 2, in particular from about 1.9 to 2, organic radicals per silicon atom, and can be prepared by known processes.
The novel polydiorganosiloxanes have an average molecular weight of at least 750, at least 50% of the organic substituents in the diorganopolysiloxane being methyl radicals and all of the other organic substituents present being monovalent hydrocarbons having from 2 to 30 carbon atoms.
Examples of suitable monovalent hydrocarbon radicals having from 2 to 30 carbon atoms are alkyl or cycloalkyl radicals, such as ethyl, propyl, butyl, n-octyl, tetradecyl, octadecyl or cyclohexyl, alkenyl radicals, such as vinyl or allyl, and aryl or aralkyl radicals, such as phenyl or tolyl.
The polydiorganosiloxanes preferably have a molecular weight of from 20,000 to 90,000.
Preferred polydiorganosiloxanes are polydimethylsiloxanes which correspond to the formula 
in which
x is from 300 to 1000, preferably from 400 to 800.
The average number of hydroxyl groups per silicon atom can be determined in the following way: 29Si-NMR spectroscopy is used to determine the ratio of the number of silicon atoms to which the hydroxyl groups are bonded, in some cases via alkylene bridges, to the number of silicon atoms to which no OH groups or radicals containing OH groups are bonded.
Suitable compounds are described, for example, in DE-B-2 459 936.
In the preparation of fabric softeners the polydiorganosiloxanes used according to the invention are preferably used in the form of aqueous emulsions. These emulsions can be prepared as follows: the polydiorganosiloxane is emulsified in water using one or more dispersants and shear forces, e.g. by means of a colloid mill. Suitable dispersants are known to the person skilled in the art, e.g. ethoxylated alcohols or polyvinyl alcohol can be used. The dispersant(s) is/are used in customary amounts known to the person skilled in the art and can be added either to the polysiloxane or to the water prior to emulsification. Where appropriate, the emulsification operation can, or in some cases, must be carried out at elevated temperature. If desired, the polydiorganosiloxane dispersions may additionally comprise dispersed polyalkylene waxes. Examples of suitable polyalkylene waxes are oxidized polyethylene waxes.
Dispersions which comprise polysiloxane and such a wax are prepared by making a dispersion of a polysiloxane by the method described above and then combining it with a dispersion of an oxidized polyethylene wax which has been prepared separately. Suitable wax dispersions are available on the market.
A polysiloxane dispersion used according to the present invention for example has the following composition:
1 to 60, preferably 5 to 25% b.w. of xcex1,xcfx89-dihydroxydimethylpolysiloxane,
0 to 20, preferably 5 to 15% b.w. of polyethylene wax,
0.5 to 15, preferably 1 to 10.0% b.w. of fatty alcohol ethoxylate (C16-C18, saturated),
0 to 5, preferably 0.1 to 2.0% b.w. of stearylamine octaethoxylate, and water ad 100%.
Examples of suitable textile fibre materials which can be treated with the novel fabric softener composition are materials made of silk, wool, polyamide or polyurethanes, and, in particular, cellulosic fibre materials of all types. Such fibre materials are, for example, natural cellulose fibres, such as cotton, linen, jute and hemp, and regenerated cellulose. Preference is given to textile fibre materials made of cotton. The novel fabric softener compositions are also suitable for hydroxyl-containing fibres which are present in mixed fabrics, for example mixtures of cotton with polyester fibres or polyamide fibres.
The invention further provides a fabric softener composition comprising
(a) a quaternary ammonium compound of the formula 
(b) a nitrogenfree polydiorganosiloxane having terminal silicon-bonded hydroxyl groups, in which
R is the aliphatic radical of tallow fatty acid, in particular a mono- or polyunsaturated aliphatic C17 radical.
Component b in the novel fabric softener composition is preferably a polydiorganosiloxane of the formula 
in which
x is from 300 to 1 000.
The fabric softener composition preferably comprises
from 1 to 20% b.w., preferably from 5 to 20% b.w., of component (a) and
from 0. 1 to 20% b.w., preferably from 0.5 to 10% b.w., of component (b).
The novel fabric softener composition may also comprise additives which are customary for standard commercial fabric softeners, for example alcohols, such as ethanol, n-propanol, i-propanol, polyhydric alcohols, for example glycerol and propylene glycol; amphoteric and nonionic surfactants, for example carboxyl derivatives of imidazole, oxethylated fatty alcohols, hydrogenated and ethoxylated castor oil, alkyl polyglycosides, for example decyl polyglucose and dodecylpolyglucose, fatty alcohols, fatty acid esters, fatty acids, ethoxylated fatty acid glycerides or fatty acid partial glycerides; also inorganic or organic salts, for example water-soluble potassium, sodium or magnesium salts, non-aqueous solvents, pH buffers, perfumes, dyes, hydrotropic agents, antifoams, antiredeposition agents, polymeric or other thickeners, enzymes, optical brighteners, antishrink agents, stain removers, germicides, fungicides, antioxidants, corrosion inhibitors and anticrease agents.
The fabric softener composition according to the invention is usually prepared by firstly stirring the active substance, i.e. the quaternary ammonium compound of the formula (1), in the molten state into water, then, where required, adding further desired additives and, finally, after cooling, adding the polydiorganosiloxane emulsion.
The fabric softener compositions according to the invention impart a soft handle to the treated textile and are readily biodegradable. The fibre materials treated with the novel fabric softener composition are very particularly characterized by good rewettability.